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Actually, the indications from previous quakes in the capital are that the land over there rose about 1 metre during the 1855 earthquake (http://geography.massey.ac.nz/staff/Hesp/PDFs/PPG99.pdf page 11) and would go up again.

According to http://www.doc.govt.nz/Community/001~For-Schools/003~Field-Trips/008~Wellington/Matiu-Somes-Island/090~Formation-Of-Wellington-Harbour.asp (don't you just love their URLs!):

Matiu/Somes, Makaro/Ward, and Mokopuna, Wellington Harbour’s three islands are peaks on a ridge formed 1.5 million years ago. The Port Nicholson basin was once some distance away from the coast and rivers and streams drained across it. The basin flooded when land south-east of the Wellington fault tilted down -Wellington Harbour (now formed) submerged the ridge and created three islands.

The harbour originally had two entrances, the present one and a channel where Kilbirnie now lies. The Miramar peninsula was an island. An earthquake in 1460 linked Miramar island with the mainland. Further uplift during the major earthquake of 1855 brought Matiu/Somes higher above sea level so that much of the present shore line is surrounded by cliffs.

I remember being told that the park in Miramar used to be a lagoon even in European times, but I can't find a source for that at the moment.

And, with regard to moving (because I know where you're going), have a look at http://www.eqc.govt.nz/commiss/105.html ;-)